A repeater is a device that receives a signal of a base station and relays the signal to a mobile communication terminal, and that is used for extending coverage in a mobile communication system. In general, the repeater receives a weak signal that is transmitted from a base station through a link antenna, amplifies the received signal, and then transmits the signal to a mobile communication terminal through a service antenna.
Nowadays, a multi band repeater that receives and relays a signal having a plurality of different frequency bands has been developed and used in the location. For example, because a dual band repeater that can simultaneously cover two bands of a code division multiple access (CDMA) system and a wideband code division multiple access (WCDMA) system shares some of parts of the CDMA repeater and the WCDMA repeater within a single equipment, a manufacturing cost is lowered and installation space is minimized.
When intensity of an input signal that is received from the base station and that is input to the repeater is greater than that of a predetermined level, because a burden is imposed on an operation of the repeater, the input signal should be lowered to an appropriate level or less. Accordingly, conventionally, by additionally providing an attenuator at the outside of the repeater, the attenuator adjusts an input signal that is received from the base station to an appropriate level and then inputs the input signal to the repeater. However, in general, because an external attenuator that is used in the repeater has a fixed attenuation value, according to the change of input signal intensity and installation environment of the repeater, in order to apply a changed attenuation value, a location operator should directly visit a location at which the repeater is installed and adjust an attenuation value. Therefore, there is a problem that much time and cost are required in maintenance of the repeater.
Further, in a multi band repeater, because intensity of an input signal that is received according to each band is different, a plurality of attenuators for attenuating each intensity of a signal that is excessively input on a band basis is required.
Further, because the multi band repeater has different propagation loss on a band basis, when the multi band repeater shares a feeder for a link antenna, an excess input state or a low input state may be formed on a frequency band basis, whereby in the multi band repeater, there is a problem that it is difficult to share a feeder of the link antenna.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.